The rule at WP:RFD#DELETE #8 is to consider deletion if it's not mentioned at the target and it's "a novel or very obscure synonym for an article name". For example, "not mentioned" is a valid reason to delete a redirect if is is a translation of the title of the article into a non-English language that is unrelated to the article's subject. Redirects should not be deleted if the connection to the subject is obvious or if the redirect is correct but not appropriate for inclusion in the article, such as {{R from brand name}}.